DESCRIPTION: Cognitive systems are representational devices, evolved to perceive the world as it usually is in the organism's natural environment. In light of this, pretend play is a very interesting activity. In pretense, the child's cognitive system purposefully thwarts reality, perceiving it as other than it actually is. Pretending is a ubiquitous activity of childhood, and at least in our own culture, parents pretend in front of children even at one year of age. The question posed in this research is why young children do not become terribly confused by pretense events. This question can be addressed at two levels. One level is what are the cognitive mechanisms that allow the child to thwart reality in this way. The second is how the child knows when to engage those mechanisms in a pretense interpretation. This research is aimed at the second question, but may shed light on the first one. The assumption is that young children somehow know to interpret pretense events as a special category, different from what is real, because certain behavioral regularities accompany pretense acts, and serve to signal to young children, "This is pretense." Those regularities may include special smiles, exaggerated, truncated, or oddly timed gestures, special linguistic forms, and special non-language sounds. This research compares parent's enactments of an event (having a snack of cereal and water) in pretense and real versions for detailing of behavioral regularities that differ in pretense events. Further experiments examine the generalizability of these regularities across acts (other types of pretense, teaching, and attention-getting), settings (home versus laboratory), addressees (of different ages), and pretenders (of different ages and genders). A second series of experiments addresses the issue of pretense comprehension in the face of all or a subset of these behavioral regularities. The work is important to our knowledge of how children construe the social world and the ubiquitous activity of pretend play. Because children with autism do not engage in spontaneous pretense, it may be useful in understanding autism as well.